字符串的所有子集

void OutPut(char *dest)
{
    for(; *dest; dest++)    cout<<*dest<<" ";
    cout<<endl;
}

void GetPowerSet(int i, char A[], char B[])
{
    if( i==strlen(A) )    OutPut(B);
    else
    {
        char x=A[i];    //GetElem
        int k=strlen(B);

        B[k]=x;        GetPowerSet(i+1, A, B);        //左子树
        B[k]='0';    GetPowerSet(i+1, A, B);        //右子树
    }
}

int main()
{
    char A[]={"123"};
    int size_B=strlen(A)+1;
    char* B=new char[size_B];
    memset(B, 0, size_B);
    GetPowerSet(0, A, B);
    delete B;
    return 0;
}

------解决方案--------------------
#1楼输出格式没有按照要求，如果要严格按照字符长度依次输出：

Java code

public class Powerset {
    public static int line = 0; 
    public static void print(String s){
        if(s.length()>line){
            System.out.format("%n%s",s);
            line++;
        }
        else {
            System.out.format(",%s",s);
        }
    }
    public static void subselect(String s,String text,int i,int k){
        if(k==0){
            print(s);
        }else{
            char c = text.charAt(i);
            
            i++;
            if(i>=text.length()){
                if(k==0)print(s);
                else if(k==1)print(s+c);                
            }else{
                subselect(s+c,text,i,k-1);
                subselect(s,text,i,k);
            }        
        }        
    }
    
    public static void solve(String text){
        char c = text.charAt(0);
        for(int k=0;k<text.length()-1;k++){
            subselect(c+"",text,1,k);
            subselect("",text,1,k+1);
        }
    }
    public static void main(String[] args) {        
        Powerset.solve("abcd");
    }

}

------解决方案--------------------
求1L给个注释，或者分析

------解决方案--------------------

探讨

C/C++ code

void OutPut(char *dest)
{
for(; *dest; dest++) cout<<*dest<<" ";
cout<<endl;
}

void GetPowerSet(int i, char A[], char B[])
{
if( i==strlen(A) ) OutPut(B);
……

------解决方案--------------------
使用递归即可
------解决方案--------------------

探讨

C/C++ code
void OutPut(char *dest)
{
for(; *dest; dest++) cout<<*dest<<" ";
cout<<endl;
}

void GetPowerSet(int i, char A[], char B[])
{
if( i==strlen(A) ) OutPut(B);
e……